TWI388115B - Power conversion drive circuit and lamp drive circuit - Google Patents

Description

Power conversion drive circuit and fluorescent tube drive circuit

The invention relates to a power conversion drive circuit, in particular to a power conversion drive circuit with an automatic shutdown and an automatic restart function.

Today's power supplies are mainly divided into linear and switched power supplies. The linear power supply has a simple circuit, small ripple, and small electromagnetic interference. However, the electronic components are large, so the circuit is bulky and heavy, and the conversion efficiency is low. Although the switching power supply is more complicated, and the chopper is relatively large and the electromagnetic interference is relatively large, due to the advantages of high conversion efficiency and low power consumption during no-load, the current power supply market is switched power supply. The device is the mainstream.

Please refer to FIG. 1A for a schematic diagram of a circuit of a switching power supply for driving a lamp. The switching power supply includes an initial resistor R, an initial capacitor C2, a Zener diode Z, a controller CON, a high-side driving capacitor C1, a high-end driving transformer T1, and a high-end transistor switch. M1, a low-end transistor switch M2, a diode D, an output capacitor C3, and a transformer T2 for converting the DC input voltage VIN into an AC output voltage VOUT to drive a lamp LAMP.

After the DC input voltage VIN is input, the current is supplied to the initial capacitor C2 through the initial resistor R, so that the voltage across the initial capacitor C2 starts to rise to be equal to the breakdown voltage of the diode Z. The initial capacitor C2 generates a drive voltage VDD to provide the power required for operation of the controller CON. When the driving voltage VDD exceeds the starting voltage value of the controller CON, the start is started to generate a signal for controlling the high-side transistor switch M1 and the low-end transistor switch M2, wherein the controller CON transmits the high-side driving capacitor C1 and the high-end driving transformer T1. The level of the control signal is raised to a suitable level to control the high side transistor switch M1. Through the switching of the high-end transistor switch M1 and the low-end transistor switch M2, the power of the DC input voltage VIN is transmitted to the output terminal to generate an AC output voltage VOUT to drive the lamp LAMP to emit light. The transformer T2 is coupled to the AC output voltage and rectified by the diode D to output power to the initial capacitor C2.

The power through the initial resistor R is greater than the power required before the controller CON has started, so that the initial capacitor C2 can be gradually stored. After the controller CON is started, power is also supplied to the controller CON through the transformer T2 and the diode D. Therefore, the initial resistance R can use a larger resistance value to reduce the power loss of the initial resistance R. However, when the circuit is abnormal, the DC input voltage VIN cannot supply power to the AC output voltage VOUT, so that the transformer T2 and the diode D cannot supply power, and the power transmitted through the initial resistor R is insufficient to provide the controller CON for normal operation. All of the power will cause problems with the operation of the controller CON.

Please refer to the first B diagram, which is a schematic diagram of the signal waveform when the switching power supply for driving the lamp is abnormal in the circuit. When the driving voltage VDD is higher than the starting voltage value UVLO, the operation starts. Since the oscillator and the control circuit inside the controller CON start to operate, the current consumed at this time is much larger than the current supplied through the resistor R through the DC input voltage VIN. The voltage of the driving voltage VDD starts to drop. When the circuit is working normally, the controller CON will output a signal to control the high-side transistor switch M1 and the low-side transistor switch M2 to switch, so that the output voltage VOUT rises and Power is supplied to the driving voltage VDD via the transformer T2 and the diode D. However, when an abnormality occurs in the circuit, the controller CON stops switching between the high-side transistor switch M1 and the low-side transistor switch M2, so that the output voltage VOUT falls and the power cannot be supplied to the driving voltage VDD, and the driving voltage VDD starts to decrease. . When the driving voltage VDD is lowered to the lowest voltage value that the controller CON can tolerate, the controller CON stops operating, so the driving voltage VDD starts to rise again above the starting voltage value UVLO, causing the controller CON to restart again, so that it is repeated until The state of the circuit anomaly is excluded. Alternatively, the conventional lamp drive circuit may cause the controller CON to constantly illuminate the lamp LAMP in order to avoid possible temporary circuit abnormalities causing the lamp LAMP to be extinguished. This process not only consumes the limit of the number of times the lamp is lit but also shortens the life of the lamp, and there is a risk of electric shock if the user replaces the lamp while forgetting to turn off the power. In addition, if the user turns off the power and then turns on the power after replacing the lamp, this avoids the risk of electric shock when the lamp is replaced, but increases the inconvenience of the user and is different from the habits of today's users.

Therefore, the conventional switching power supply has a problem of constantly restarting when the circuit is abnormal, which not only causes the life of the circuit component to be reduced, but also causes inconvenience to the user or has a safety concern.

In view of the problems described in the prior art, the power conversion drive circuit of the present invention turns off the power conversion drive circuit when the driven load does not exist to reduce the possible power consumption of the control circuit in the power conversion drive circuit for continuous operation when the circuit is abnormal. And also Users can avoid the safety concerns. In addition, when the user replaces the load, the power conversion drive circuit will automatically restart to increase user convenience.

To achieve the above object, the present invention provides a power conversion drive circuit including a conversion circuit, a control circuit and a load circuit. The conversion circuit is coupled to an input voltage, and the control circuit is coupled to the conversion circuit for controlling the conversion circuit to convert the input voltage into an output voltage. The load circuit includes a load detecting unit and a load, the load is coupled to the output voltage, and the load detecting unit is coupled to a detecting voltage source. The load detection unit generates a load detection signal when the load circuit is inserted into the power conversion drive circuit, so that the control circuit is restarted.

In this way, by detecting the insertion of the load circuit to restart the control circuit, the advantage of automatic restart can be achieved.

The invention also provides another power conversion driving circuit, comprising a conversion circuit, a control circuit and a load circuit. The conversion circuit is coupled to an input voltage, and the control circuit is coupled to the conversion circuit for controlling the conversion circuit to convert the input voltage into an output voltage. The load circuit includes a load detecting unit and a load, the load is coupled to the output voltage, and the load detecting unit is coupled to a driving voltage source. The control circuit is coupled to the driving voltage source through the load detecting unit to receive the power required for operation, and when the load circuit is removed, the power required to operate the control circuit is stopped.

The invention further provides a fluorescent tube driving circuit comprising a conversion circuit, a control circuit and a load circuit. The conversion circuit is coupled to an input voltage, and the control circuit is coupled to the conversion circuit for controlling the conversion circuit to convert the input voltage into an output voltage. The load circuit includes a load detecting unit and a fluorescent tube, wherein the fluorescent light The lamp is coupled to the output voltage and has two filaments. The load detection unit couples the input voltage and the ground through the two filaments to generate a load detection signal. The control circuit stops when the circuit of the fluorescent lamp driving circuit is abnormal, and restarts when detecting that the load detecting signal enters a predetermined voltage range.

In this way, when the load circuit is removed, the power required to supply the control circuit is stopped, and the control circuit can be turned off due to insufficient driving voltage to reduce the power consumption of the control circuit. Moreover, when the load circuit is reinserted to provide the power required by the control circuit again, the control circuit will be restarted, and the advantage of automatic restart can also be achieved.

The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings.

Please refer to the second figure, which is a circuit block diagram of a power conversion driving circuit according to the present invention. The power conversion drive circuit includes a control circuit 100, a conversion circuit 160, and a load circuit 180. The conversion circuit 160 is coupled to an input voltage VIN. The control circuit 100 is coupled to the conversion circuit 160 to generate a control signal S to control the conversion circuit 160 to convert the input voltage VIN into an output voltage VOUT. The load circuit 180 includes a load 182 and a load detecting unit 185. The load 182 is coupled to the output voltage VOUT. The load detecting unit 185 is coupled to a detecting voltage source VDE. The detecting voltage source VDE can be an input voltage VIN and an output voltage. VOUT or other voltage source that can provide power. The load detection unit 185 generates a load detection signal Sre when coupled to the detection voltage source VDE. Therefore, when the load circuit 180 is inserted into the power conversion drive circuit, the control circuit 100 can receive the load detection signal Sre generated by the load detection unit 185 and restart.

It should be noted that the power conversion driving circuit of the present invention can provide electrical isolation in accordance with the requirements of safety regulations. Referring to the second figure, one side of the conversion circuit 160 is coupled to the input voltage VIN and a first common potential G1. After the conversion, the output voltage VOUT is generated on the other side, and the side is coupled to a second common potential G2. . One end of the load receives the output voltage VOUT and the other side is coupled to the second common potential G2. The control circuit 100 and the load detection unit 185 are coupled to the first common potential G1. Therefore, the load 182 and the load detecting unit 185 in the load circuit 180 are not directly connected to each other and are respectively coupled to the corresponding common potential to achieve the effect of electrical isolation. Of course, if the electrical isolation is not required in practical applications, the load 182 and the load detecting unit 185 can be connected to each other.

Next, please refer to the third figure, which is a circuit diagram of a power conversion driving circuit according to a first preferred embodiment of the present invention. The power conversion drive circuit includes a control circuit 200, a conversion circuit 260, and a load circuit 280. The conversion circuit 260 is a DC-DC converter circuit including an inductor L, a diode D, a switch SW and an output regulator capacitor Co for receiving an input voltage VIN and boosting the output to a voltage VOUT. . The load circuit 280 includes a light emitting diode module 282 and a load detecting unit 285. The LED module 282 is coupled to the conversion circuit 260 via a first connection terminal a1 of the load circuit 280 to receive the output voltage VOUT and is coupled to the second connection terminal a2 of the load circuit 280. The load detection module 285 includes a resistor, and one end of the first connection terminal a1 is coupled to the conversion circuit 260 to use the output voltage VOUT as a detection voltage source. The other end is coupled to a third connection terminal a3 of the load circuit 280 through a resistor 290a and generates a load detection signal Sre.

The control circuit 200 includes a voltage under-locking unit 205, a restart unit 210, a current feedback unit 215, an over-temperature protection unit 230, a voltage feedback unit 235, a protection unit 240, and a drive signal generation unit 245. The switching of the changeover switch SW in the control signal control conversion circuit 260 is generated. The voltage under-locking unit 205 is coupled to a driving voltage VDD. After the driving voltage VDD reaches a predetermined operating voltage, an activation signal UVLO is generated to other circuit units in the control circuit 200, so that other circuit units start the starting operation.

The power conversion driving circuit includes a current detecting circuit 270 and a voltage detecting circuit 275. The current detecting circuit 270 is coupled to the load circuit 280 to detect a load current flowing through the light emitting diode module 282 and generate A current detection signal IFB is coupled to the conversion circuit 260 to detect the output voltage VOUT and generate a voltage detection signal VFB. The current feedback unit 215 receives the current detection signal IFB to generate a pulse width control signal PWM, and generates an overcurrent protection signal OCP when the load current exceeds a predetermined current upper limit value. The voltage feedback unit 235 receives the voltage detection signal VFB, and generates an overvoltage protection signal OVP when the output voltage VOUT exceeds a predetermined voltage upper limit value. The over temperature protection unit 230 detects the temperature of the LED module 282 and generates an over temperature protection signal OTP when the temperature exceeds a predetermined temperature upper limit. The protection unit 240 is coupled to the current feedback unit 215, the over temperature protection unit 230, the voltage feedback unit 235, and the current detection circuit 270, and receives the overvoltage protection signal OVP, the overcurrent protection signal OCP, and the over temperature protection signal OTP. At one time, a protection signal PROT is generated to the driving signal generating unit 245 to stop the driving signal generating unit 245 from generating a control signal. The driving signal generating unit 245 receives the pulse width control signal PWM, and adjusts the duty cycle of the control signal accordingly to control the power level of the input voltage VIN to be transmitted to the conversion circuit 260, so that the load current flowing through the LED module 282 is stabilized. At a predetermined current value, the LED module 282 is stably illuminated. When the driving signal generating unit 245 receives the protection signal PROT, it immediately stops outputting the control signal until the protection signal PROT is no longer received. If the circuit abnormality causes the protection unit 240 to receive the overvoltage protection signal OVP or the overcurrent protection signal OCP for a predetermined time, or for a predetermined time, the current detection signal IFB is zero (ie, the load current is zero for a predetermined time) The protection unit 240 generates and continuously outputs the protection signal PROT to stop the control circuit 200 from controlling the conversion circuit 260 and locking in the protection mode until the control circuit 200 is restarted.

When the load 282 is abnormal, the control circuit 200 will stop outputting the control signal, and the output voltage VOUT will gradually decrease due to the leakage current of the circuit until the input voltage VIN is turned on to turn on the diode D, and the output voltage VOUT is at this time. It will remain at a bias voltage biased below the input voltage VIN. The restart unit 210 is coupled to the load detection unit 285 to receive the load detection signal Sre. Since the load detection unit 285 is built into the load circuit 280, when the load 282 is abnormal and the user removes the load circuit 280 for replacement, the load detection unit 285 will be removed along with the load circuit 280. At this time, through the resistor 290a, the load detection signal Sre is at a low level. The restart unit 210 enters a preliminary restart state. When the new load circuit 280 is inserted into the power conversion drive circuit, the load detection unit 285 recouples the third connection terminal a3 to the output voltage VOUT. Therefore, when the new load circuit 280 is inserted into the power conversion drive circuit, the load detection signal Sre rises again above a restart potential. At this time, the restart unit 210 outputs a restart signal Reset to cause the protection unit 240 to be unlocked, and the control circuit 200 is restarted.

Next, please refer to the fourth figure, which is a circuit diagram of a power conversion drive circuit according to a second preferred embodiment of the present invention. The power conversion drive circuit includes a control circuit 300, a conversion circuit 360, and a load circuit 380. The conversion circuit 360 is a reverse conversion circuit including a transformer T, a first diode D1, a second diode D2, a switch SW1 and an output voltage regulator Co for receiving an input voltage. VIN is boosted and converted to an output voltage VOUT. The input voltage VIN is generated by an AC voltage source VAC rectified by a bridge rectifier BD and stabilized by an input voltage stabilizing capacitor Cin. The transformer T has a primary side coil L1, a primary side coil L3, and an auxiliary coil L2. One end of the primary side coil L1 is coupled to the input voltage VIN, and the other side is coupled to the switch SW1. The secondary side coil L3 is coupled to the first diode D1 for rectification, and is regulated by the output voltage stabilizing capacitor Co to an output voltage VOUT. The auxiliary coil L2 passes through the second diode D2 to transfer part of the power stored in the transformer T to the control circuit 300.

The load circuit 380 includes a light emitting diode module 382 and a load detecting unit 385. The LED module 382 includes a plurality of LEDs 382a and 382b and a current sharing circuit 384. The current sharing circuit 384 is coupled to the plurality of LEDs 382a and 382b to flow through substantially the same current and through the load. One of the circuits 380 is connected to the second connection terminal b2. In this embodiment, the load detecting unit 385 is a power line coupled to one of the first connection end point b1 and the third connection end point b3 of the load circuit 380, and has a resistance of almost zero. One end of the load detecting unit 385 is coupled to the input voltage VIN through a resistor 390a, and the load detecting signal Sre is generated at the other end.

The power conversion driving circuit includes an input driver 350 having a starting capacitor Cs, a Zener diode ZD and a starting resistor Rs for receiving the input voltage VIN and converting it into a driving voltage VDD to the control circuit 300. The control circuit 300 includes a voltage under-locking unit 305, a restart unit 310, a current limiting unit 320, an over-temperature protection unit 330, a voltage feedback unit 335, a protection unit 340, and a driving signal generating unit 345. Switching of the changeover switch SW1 in the control signal control conversion circuit 360 is generated. The voltage under-locking unit 305 is coupled to a driving voltage VDD. After the driving voltage VDD reaches a predetermined starting voltage, an activation signal UVLO is generated to the other circuit units in the control circuit 300, so that other circuit units start the starting operation.

The power conversion driving circuit includes a voltage detecting circuit 375 and a current limiting resistor 365. The current limiting resistor 365 is coupled to the switching switch SW1 in the conversion circuit 360 to generate a current signal Ise according to the magnitude of the current flowing through the switching switch SW1. The current limiting unit 320 receives the current signal Ise, and generates a current limiting signal Ili to the driving signal generating unit 345 when the current flowing through the switching switch SW1 exceeds a current limiting value. The voltage detection circuit 375 is coupled to the conversion circuit 360 to detect the output voltage VOUT and generate a voltage detection signal VFB. The voltage feedback unit 335 receives the voltage detection signal VFB to generate a pulse width control signal PWM, and generates an overvoltage protection signal OVP when the output voltage exceeds a predetermined voltage upper limit value. The over temperature protection unit 330 detects the temperature of the LED module 382 and generates an over temperature protection signal OTP when the temperature exceeds a predetermined temperature upper limit. The protection unit 340 is coupled to the over-temperature protection unit 330 and the voltage feedback unit 335. When receiving any of the over-voltage protection signal OVP and the over-temperature protection signal OTP, a protection signal PROT is generated to the driving signal generating unit 345 to stop the driving signal. The generating unit 345 generates a control signal. The driving signal generating unit 345 receives the pulse width control signal PWM, and adjusts the duty cycle of the control signal to control the power level of the input voltage VIN to the conversion circuit 360. The output voltage VOUT is stabilized at a predetermined voltage value, and is When the current limiting signal Ili is received during the switching cycle, the switching switch SW1 is immediately turned off until the end of the switching period to avoid the switching current flowing through the large current. When the driving signal generating unit 345 receives the protection signal PROT, it immediately stops outputting the control signal until the protection signal PROT is no longer received. If the circuit abnormality causes the protection unit 340 to receive the overvoltage protection signal OVP for a predetermined time, the protection unit 340 generates and continuously outputs the protection signal PROT to stop the control circuit 300 from controlling the conversion circuit 360 and locking in the protection mode until the control circuit 300 is Restart it.

The restart unit 310 is coupled to the load detection unit 385 to receive the load detection signal Sre. Since the load detection unit 385 is built into the load circuit 380, when the load 382 is abnormal and the user removes the load circuit 380 for replacement, the load detection unit 385 will be removed along with the load 380. At this time, the load detection signal Sre is at a low level, and the restart unit 310 enters a preliminary restart state. When the new load circuit 380 is inserted into the power conversion drive circuit, the load detection unit 385 is coupled to the input voltage VIN through the resistor 390a. Therefore, when the new load circuit 380 is inserted into the power conversion drive circuit, the load detection signal Sre rises again above a restart potential. At this time, the restart unit 310 outputs a restart signal Reset to cause the protection unit 340 to unlock the state, and the control circuit 300 is restarted.

Please refer to FIG. 5, which is a circuit diagram of a power conversion driving circuit according to a third preferred embodiment of the present invention. The power conversion drive circuit includes a control circuit 400, a conversion circuit 460, and a load circuit 480. The conversion circuit 460 is a full-bridge DC-to-AC conversion circuit. The primary side is coupled to a first common circuit G1, and the secondary side is coupled to a second common circuit G2 for converting the DC input voltage VIN into an AC. The voltage VO is output to drive a fluorescent tube 482 in the load circuit 480. The load circuit 480 includes a fluorescent tube 482 and a load detecting unit 485. The fluorescent tube 482 is coupled to the AC output voltage VO and the second common through a first connection end c1 and a second connection end c2. The potential detecting unit 485 is coupled to an input starter 450 and a first common potential G1 via a third connection terminal c3 and a fourth connection terminal c4, and generates a load detection signal Sre. Since the load detection unit 485 is coupled to the input voltage VIN via a resistor 490a, when the load circuit 480 is removed, the level of the load detection signal Sre rises to the level of the input voltage VIN when the load circuit 480 is inserted. The level of the load detection signal Sre will decrease. In addition, since the common potentials of the fluorescent tube 482 and the load detecting unit 485 are different and are not directly connected, they are electrically isolated from each other.

The power conversion drive circuit further includes an input enabler 450. Both the input enabler 450 and the control circuit 400 are coupled to the first common potential G1. Input starter 450 receives and loses The voltage VIN is input and converted into a driving voltage VDD to the control circuit 400. The control circuit 400 includes a voltage under-locking unit 405, a current feedback unit 415, an oscillating unit 416, a voltage limiting unit 435, a protection unit 440, and a driving signal generating unit 445 for generating a control signal control conversion circuit 460. Switching of the switch in the middle. The voltage under-locking unit 405 is coupled to a driving voltage VDD. After the driving voltage VDD reaches a predetermined starting voltage, an activation signal UVLO is generated to other circuit units in the control circuit 400, so that other circuit units start the starting operation.

The power conversion driving circuit includes an electrically isolated current detecting circuit 470 and an electrically isolated voltage detecting circuit 475, which may be an optical coupler or other electrically isolated components. The electrically isolated current detecting circuit 470 is coupled to the fluorescent tube 482 to detect the current of the tube flowing through the fluorescent tube 482 and generate a current detecting signal IFB. The electrical isolation voltage detection circuit 475 is coupled to the conversion circuit 460 to detect the amplitude of the AC output voltage VOUT and generate a voltage detection signal VFB. The oscillating unit 416 receives the current detecting signal IFB and generates an oscillating signal OSC. The oscillating unit 416 oscillates the signal OSC when the current detecting signal IFB represents the lamp current is zero, and outputs the higher frequency oscillating signal OSC to illuminate the fluorescent tube 482; when the current detecting signal IFB represents the tube current is greater than zero (Represents that the fluorescent tube 482 is lit), and outputs a lower frequency oscillation signal OSC. The current feedback unit 415 receives the current detection signal IFB and the oscillation signal OSC to generate a pulse width control signal PWM, and generates a lamp undercurrent protection signal UCP when the lamp current continues for a predetermined time. The voltage limiting unit 435 receives the voltage detection signal VFB, and generates a voltage limiting signal Vli when the output voltage VO exceeds a predetermined voltage upper limit value. Drive signal generating unit 445 receives pulse width Controlling the signal PWM, and adjusting the duty cycle of the control signal accordingly to control the power level of the input voltage VIN to the conversion circuit 460, so that the lamp current is stabilized at a predetermined current value, and when the voltage limiting signal Vli is received, The voltage feedback control is such that the voltage across the fluorescent tube 482 during the lighting process is not too high.

The protection unit 440 is coupled to the current feedback unit 415, the oscillating unit 416, and the voltage limiting unit 435, and determines whether the lamp undercurrent protection signal UCP or the voltage limiting signal Vli continues to be generated for more than a predetermined time according to the oscillating signal OSC. A protection signal PROT is generated to the driving signal generating unit 445 to stop the driving signal generating unit 445 to generate a control signal and lock until the control circuit 400 is restarted.

The input enabler 450 includes a switch SW3. In the present embodiment, the switch SW3 is a P-type MOS. When the load circuit 480 is removed, the level of the load detection signal Sre rises to the level of the input voltage VIN, so that the switch SW3 is turned off, and the driving voltage VDD starts to drop. When the driving voltage VDD is too low to cause the voltage under-locking unit 405 to generate an activation signal UVLO to other circuit units in the control circuit 400, the control circuit 400 stops operating. When the load circuit 480 is reinserted, the load detection signal Sre potential drops to turn on the switch SW3, and the driving voltage VDD rises again to cause the voltage under-locking unit 405 to generate an activation signal UVLO again, and the control circuit 400 automatically restarts.

Please refer to a sixth diagram, which is a circuit diagram of a power conversion driving circuit according to a fourth preferred embodiment of the present invention. The power conversion drive circuit includes a control circuit 500, an input enable circuit 550, a conversion circuit 560, a current detection circuit 570 and a voltage detection circuit 575, a load circuit 580, and a frequency adjustment circuit 595. Conversion The circuit 560 is a constant-current AC conversion circuit. The primary side is coupled to the DC input voltage VIN and converted to an AC output voltage VO on the secondary side to drive a fluorescent tube 582 in the load circuit 580. A diode is rectified to provide power to the input enable circuit 550. The input enable circuit 550 is coupled to the auxiliary input side of the DC input voltage VIN and the conversion circuit 560. When the power conversion drive circuit is not operating, the power of the DC input voltage VIN is received to provide a driving voltage VDD to the control circuit 500 for power conversion driving. When the circuit is in operation, it also receives power from the auxiliary side. The load circuit 580 includes a fluorescent tube 582 and a load detecting unit 585. The fluorescent tube 582 has a first filament 582a and a second filament 582b. One end of the first filament 582a and one end of the second filament 582b The other end of the first filament 582a is coupled to the AC output voltage VO via a first connection terminal d1 and coupled to the DC input voltage VIN through the resistor 590a. The other end of the second filament 582b is coupled. It is coupled to the ground through a second connection terminal d2. The control circuit 500 receives a current detection signal IFB generated by the current detection circuit 570 and a voltage detection signal VFB generated by the voltage detection circuit 575 to generate a power conversion of the control signal control conversion circuit 560.

The control circuit 500 includes a voltage under-locking unit 505, a lamp protection restart unit 510, a current feedback unit 515, an oscillating unit 516, an over-temperature protection unit 530, a voltage feedback unit 535, and a protection unit 540. And a driving signal generating unit 545 for generating switching of the switching switch in the control signal control conversion circuit 560. The voltage under-locking unit 505 is coupled to the input enable circuit 550 to receive the driving voltage VDD. After the driving voltage VDD reaches a predetermined operating voltage, an activation signal UVLO is generated to the current feedback unit 515, the over-temperature protection unit 530, and the voltage feedback unit. 535. The protection unit 540 and the driving signal generating unit 545 enable the circuit units to start the starting operation.

The current detecting circuit 570 is coupled to the load circuit 580 to detect a load current flowing through the fluorescent tube 582 and generate a current detecting signal IFB. The voltage detecting circuit 575 is coupled to the converting circuit 560 to detect the output. The voltage VO generates a voltage detection signal VFB. The oscillating unit 516 generates an oscillating signal OSC. At the beginning of the circuit, the frequency of the oscillating signal OSC is maintained at a higher frequency for a warm-up time to preheat the fluorescent tube 582, and then the frequency is performed at a lower operating frequency. The frequency sweeps to illuminate the fluorescent tube 582 and thereafter maintains the frequency at the operating frequency. The current feedback unit 515 receives the current detection signal IFB and the oscillation signal OSC to generate a pulse width control signal PWM, and generates an overcurrent protection signal OCP when the load current exceeds a predetermined current upper limit value. The voltage feedback unit 535 receives the voltage detection signal VFB, and generates an overvoltage protection signal OVP when the output voltage VO exceeds a predetermined voltage upper limit value. The lamp protection restarting unit 510 is coupled to the load detecting unit 585 for detecting whether the first filament 582a and the second filament 582b of the fluorescent tube 582 are damaged or whether the fluorescent tube 582 is removed, and if so, generating a Lamp protection signal LD. The over temperature protection unit 530 detects the temperature of the control circuit 500 and generates an over temperature protection signal OTP when the temperature exceeds a predetermined temperature upper limit. The protection unit 540 is coupled to the oscillating unit 516, the lamp protection restart unit 510, the current feedback unit 515, the over temperature protection unit 530, the voltage feedback unit 535, and the current detection circuit 570 for receiving the overvoltage protection signal OVP and overcurrent. When any one of the protection signal OCP, the lamp protection signal LD and the over-temperature protection signal OTP, a protection signal PROT is generated to the drive signal generation unit 545 to stop the drive signal generation unit 545 from generating a control signal. The driving signal generating unit 545 receives the pulse width control signal PWM, and adjusts the duty cycle of the control signal accordingly to control the power level of the DC input voltage VIN to be transmitted to the conversion circuit 560, so that the fluorescent tube 582 is stably illuminated. When the driving signal generating unit 545 receives the protection signal PROT, it immediately stops outputting the control signal until the protection signal PROT is no longer received. If the circuit abnormality causes the protection unit 540 to receive the overvoltage protection signal OVP or the overcurrent protection signal OCP for a predetermined time, or the current detection signal IFB is zero for a predetermined time, the protection unit 540 determines according to the oscillation signal OSC. When the above circuit abnormality occurs, the protection signal PROT is generated and continuously outputted to stop the control circuit 500 from controlling the conversion circuit 560 and locked in the protection mode until the control circuit 500 is restarted.

The load circuit 580 is mounted on the power conversion drive circuit, and the load detection unit 585 is coupled to the DC input voltage VIN to generate and generate a load detection signal Sre. At this time, the potential of the load detection signal Sre falls on the lamp protection restart unit. Between a first reference potential V1 and a second reference potential V2 in 510, wherein the first reference potential V1 is higher than the second reference potential V2. When the load circuit 580 is removed or the first filament 582a of the fluorescent tube 582 is broken and opened, the load detection signal Sre is coupled to the ground by a load detection initial circuit 590 to make the potential of the load detection signal Sre Below the second reference potential V2. When the second filament 582b of the fluorescent tube 582 is broken and opened, the load detection signal Sre is coupled to the DC input voltage VIN by a resistor 590a and higher than the first reference potential V1. The lamp protection restart unit 510 includes a first comparator 511, a second comparator 512, an OR gate 513, and a delay circuit 514. The first comparator 511 and the second comparator are configured to compare whether the load detection signal Sre falls between the first reference potential V1 and a second reference potential V2. When the load detection signal Sre is higher than the first reference potential V1 or lower than the second reference potential V2, the first comparator 511 or the second comparator 512 generates a high-level output to the gate 513, causing the gate 513 to be generated. The lamp protection signal LD to the protection unit 540 causes the control circuit 500 to enter the protection mode.

In addition, when the delay circuit 514 receives the protection signal PROT, it is activated to determine whether the abnormal state of the fluorescent tube 582 has been released. When the abnormal state of the fluorescent tube 582 is released, for example, the user replaces the new fluorescent tube 582, or the gate 513 outputs a low level output signal. When the delay circuit 514 continues to receive the low level output signal of the gate 513 for a predetermined time, a restart signal Reset is generated to the protection unit 540 to cause the protection unit 540 to be unlocked, and the control circuit 500 is restarted.

The oscillating unit 516 can be coupled to a frequency adjusting circuit 595 to adjust the operating frequency of the control circuit 500, that is, the frequency of the oscillating signal OSC. As shown in the sixth figure, the frequency adjustment circuit 595 is a current mirror structure comprising two bipolar transistors connected to the base. The emitters of the two bipolar transistors are grounded, and the bipolar transistors connected to the base are transmitted through the bipolar transistor. A frequency adjustment resistor Rfadj is connected to the driving voltage VDD (or other constant voltage source) to flow through a frequency adjustment current Ifajj, and is generated by another bipolar transistor image and input to the oscillation unit 516 to adjust the charging and discharging of the oscillation unit 516. The magnitude of the current, which in turn changes the frequency of the oscillating signal OSC. The frequency adjustment circuit 595 can achieve the function of dimming. In this embodiment, the adjustment frequency adjustment resistor Rfadj is an adjustable resistor, and the user adjusts the resistance value of the frequency adjustment resistor Rfadj to determine the frequency adjustment current. The Ifadj size, in turn, adjusts the operating frequency of circuit 500. When the frequency is increased, the power received by the fluorescent tube 582 will decrease and the brightness will be darkened. When the frequency is lowered, the power received by the fluorescent tube 582 will rise and the brightness will become brighter.

When the frequency adjustment circuit 595 is connected to the input voltage VIN, it has a function of adjusting the output power with the input voltage VIN. When the input voltage VIN is high (for example, provided by the 220V mains after rectification), the frequency adjustment current Ifajj will rise to increase the frequency to compensate for the output power of the input voltage VIN rising, and vice versa. The frequency adjustment circuit 595 is only one of the means for adjusting the frequency by adjusting the charging and discharging current. In actual application, the circuit structure of the oscillating unit 516 can be matched. For example, the voltage of the internal upper and lower reference voltages can be adjusted or generated for the voltage controlled oscillator. The value of the capacitance of the ramp signal.

Therefore, as shown in the above embodiment, the power conversion drive circuit of the present invention turns off the power conversion drive circuit when the driven load is applied to reduce the possible power consumption of the control circuit in the power conversion drive circuit for continuous operation when the circuit is abnormal, and also Users can avoid the safety concerns. In addition, when the user replaces the load, the power conversion drive circuit will automatically restart to increase user convenience.

As described above, the present invention fully complies with the three requirements of the patent: novelty, advancement, and industrial applicability. The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of the invention is defined by the scope of the following claims.

Prior art:

R. . . Initial resistance

C2. . . Initial capacitance

Z. . . Accumulator diode

CON. . . Controller

C1. . . High-end drive capacitor

T1. . . High-end drive transformer

M1. . . High-end transistor switch

M2. . . Low-end transistor switch

D. . . Dipole

C3. . . Output capacitor

T2. . . transformer

VIN. . . Input voltage

VOUT. . . The output voltage

LAMP. . . Lamp

this invention:

100, 200, 300, 400, 500. . . Control circuit

160, 260, 360, 460, 560. . . Conversion circuit

180, 280, 380, 480, 580. . . Load circuit

182. . . load

185, 285, 385, 485, 585. . . Load detection unit

205, 305, 405, 505. . . Low voltage lock unit

210, 310. . . Restart unit

215, 515. . . Current feedback unit

230, 330, 530. . . Over temperature protection unit

235, 335, 535. . . Voltage feedback unit

240, 340, 440, 540. . . Protection unit

245, 345, 445, 545. . . Drive signal generation unit

270, 570. . . Current detection circuit

275, 375, 575. . . Voltage detection circuit

282. . . Light-emitting diode module

290a, 390a, 490a, 590a. . . resistance

320. . . Current limiting unit

350, 450, 550. . . Input initiator

365. . . Current limiting resistor

382a, 382b. . . Light-emitting diode

384. . . Current sharing circuit

416, 516. . . Oscillating unit

470. . . Electrically isolated current detection circuit

475. . . Electrically isolated voltage detection circuit

482, 582. . . Fluorescent tube

510. . . Lamp protection restart unit

511. . . First comparator

512. . . Second comparator

513. . . Gate

514. . . Delay circuit

590. . . Load detection initial circuit

595. . . Frequency adjustment circuit

Rfadj. . . Frequency adjustment resistor

OSC. . . Concussion signal

Ise. . . Current signal

VIN. . . Input voltage

S. . . Control signal

VOUT. . . The output voltage

VDE. . . Detecting voltage source

Sre. . . Load detection signal

G1. . . First common potential

G2. . . Second common potential

L. . . inductance

D, D1, D2. . . Dipole

SW, SW1. . . Toggle switch

A1, b1, c1, d1. . . First connection endpoint

A2, b2, c2, d2. . . Second connection endpoint

A3, b3, c3. . . Third connection endpoint

C4. . . Fourth connection endpoint

VFB. . . Voltage detection signal

IFB. . . Current detection signal

PWM. . . Pulse width control signal

OCP. . . Overcurrent protection signal

OVP. . . Overvoltage protection signal

OTP. . . Over temperature protection signal

PROT. . . Protection signal

T. . . transformer

BD. . . Bridge rectifier

VAC. . . AC voltage source

L1. . . Primary side coil

L2. . . Secondary side coil

L3. . . Auxiliary coil

UVLO. . . Start signal

Cs. . . Start capacitor

ZD. . . Kina diode

Rs. . . Startup resistor

Ili. . . Current limiting signal

Cin. . . Input regulator capacitor

Reset. . . Restart signal

UCP. . . Lamp undercurrent protection signal

Vli. . . Voltage limiting signal

SW3. . . switch

582a. . . First filament

582b. . . Second filament

VO. . . AC output voltage

LD. . . Lamp protection signal

V1. . . First reference potential

V2. . . Second reference potential

The first A diagram is a schematic circuit diagram of a conventional switching power supply for driving a lamp.

The first B is a schematic diagram of the signal waveform of a conventional switching power supply for driving a lamp when the circuit is abnormal.

The second figure is a circuit block diagram of a power conversion drive circuit in accordance with the present invention.

The third figure is a circuit diagram of a power conversion drive circuit in accordance with a first preferred embodiment of the present invention.

The fourth figure is a circuit diagram of a power conversion drive circuit in accordance with a second preferred embodiment of the present invention.

Figure 5 is a circuit diagram of a power conversion drive circuit in accordance with a third preferred embodiment of the present invention.

Figure 6 is a circuit diagram of a power conversion drive circuit in accordance with a fourth preferred embodiment of the present invention.

100. . . Control circuit

160. . . Conversion circuit

180. . . Load circuit

182. . . load

185. . . Load detection unit

VIN. . . Input voltage

S. . . Control signal

VOUT. . . The output voltage

VDE. . . Detecting voltage source

Sre. . . Load detection signal

G1. . . First common potential

G2. . . Second common potential

Claims (29)

A power conversion drive circuit includes: a conversion circuit coupled to an input voltage; a control circuit coupled to the conversion circuit for controlling the conversion circuit to convert the input voltage into an output voltage; and a load circuit including a a load detecting unit and a load, the load is coupled to the output voltage, and the load detecting unit is coupled to a detecting voltage source; wherein the load detecting unit generates a load when the load circuit is inserted into the power conversion driving circuit The signal is detected to restart the control circuit. The power conversion drive circuit of claim 1, wherein the detection voltage source is the input voltage or the output voltage. The power conversion drive circuit of claim 2, wherein the conversion circuit is a DC-DC conversion circuit, the load is a light-emitting diode module, and the control circuit is based on a voltage representative of the output voltage. The test signal controls the conversion circuit. The power conversion drive circuit of claim 3, wherein the control circuit controls the conversion circuit according to a current detection signal representing one of load currents flowing through the load. The power conversion drive circuit of claim 4, wherein the control circuit comprises a protection unit, the protection unit stops when the output voltage exceeds a predetermined protection voltage value or when the load current exceeds a predetermined protection current value. The control circuit controls the conversion circuit and locks it. The power conversion drive circuit of claim 5, wherein the protection unit is unlocked when receiving the load detection signal. The power conversion drive circuit of claim 2, wherein the conversion circuit is a continuous AC conversion circuit, the load is a fluorescent tube, and the control circuit detects a signal according to a voltage representative of the output voltage. And controlling the conversion circuit on behalf of a current detection signal flowing through one of the load currents of the load. The power conversion drive circuit of claim 7, wherein the control circuit comprises a protection unit, wherein the protection unit exceeds a predetermined protection voltage value, the load current exceeds a predetermined protection current value or the load When the current is lower than a predetermined current value, the control circuit stops the control circuit and locks. The power conversion drive circuit of claim 8, wherein the protection unit is unlocked when receiving the load detection signal, so that the control circuit is restarted. The power conversion drive circuit of claim 1, wherein the load detection unit is not directly connected to the load. The power conversion drive circuit of claim 10, further comprising an input enabler coupled to the input voltage to generate a driving voltage, the control circuit coupling the driving voltage to receive an operation required electric power. The power conversion drive circuit of claim 1, further comprising a frequency adjustment circuit for adjusting an operating frequency of the control circuit to adjust a power outputted by the conversion circuit to the load. The power conversion drive circuit of claim 12, wherein the frequency adjustment circuit is coupled to the input voltage such that the operating frequency varies with the input voltage. A power conversion drive circuit includes: a conversion circuit coupled to an input voltage; a control circuit coupled to the conversion circuit for controlling the conversion circuit to convert the input voltage into an output voltage; and a load circuit including a a load detecting unit and a load, the load is coupled to the output voltage, the load detecting unit is coupled to a driving voltage source, wherein the control circuit is coupled to the driving voltage source through the load detecting unit to receive an operation required Power, when the load circuit is removed, stops providing the power required for operation of the control circuit. The power conversion drive circuit of claim 14, further comprising an input enabler coupled to the input voltage to generate a driving voltage, the control circuit coupling the driving voltage to receive the operation required electric power. The power conversion drive circuit of claim 15, wherein the input enabler comprises a switch component coupled to the load detection unit for transmitting power required for the operation, and stopping transmission when the load circuit is removed. The power required for this operation. The power conversion drive circuit of claim 16, wherein the conversion circuit comprises a transformer having a primary side coil, a secondary side coil and an auxiliary coil, wherein the primary side coil is coupled to the input voltage The secondary side coil is coupled to the output voltage, and the auxiliary coil is coupled to the input starter. The power conversion drive circuit of claim 16, wherein the driving voltage source is the input voltage, and the input enabler couples the input voltage through the load detecting unit. The power conversion drive circuit of claim 14, wherein the load detection unit is not directly connected to the load. The power conversion drive circuit of claim 14, wherein the load detection unit and the load are electrically isolated from each other. The power conversion drive circuit of claim 14, further comprising a frequency adjustment circuit for adjusting an operating frequency of the control circuit to adjust a power outputted by the conversion circuit to the load. The power conversion drive circuit of claim 21, wherein the frequency adjustment circuit is coupled to the input voltage such that the operating frequency varies with the input voltage. A fluorescent lamp driving circuit comprises: a conversion circuit coupled to an input voltage; a control circuit coupled to the conversion circuit for controlling the conversion circuit to convert the input voltage into an output voltage; and a load circuit The device includes a load detecting unit and a fluorescent tube. The fluorescent tube is coupled to the output voltage and has two filaments. The load detecting unit couples the input voltage and the ground through the two filaments to generate a load detection. The control circuit stops when the circuit of the fluorescent lamp driving circuit is abnormal, and restarts after detecting that the load detecting signal enters a predetermined voltage range. The fluorescent tube driving circuit of claim 23, wherein the control circuit comprises a protection unit, wherein the protection unit exceeds a predetermined protection voltage value or the load current exceeds a predetermined protection current value Or when the load current is lower than a predetermined current value, a protection signal is generated to stop the operation of the control circuit. The fluorescent tube driving circuit of claim 24, wherein the control circuit comprises a restarting unit, the restarting unit is activated when receiving the protection signal, and then detecting that the load detection signal enters The predetermined voltage range generates a restart signal to restart the control circuit. The fluorescent lamp driving circuit of claim 25, wherein the restarting unit comprises a first comparator and a second comparator for determining whether the load detection signal enters the predetermined voltage range. The fluorescent lamp driving circuit of claim 26, wherein the restarting unit further comprises a delay circuit for generating the restart after determining that the load detecting signal enters the predetermined voltage range for a predetermined length of time. Signal. The fluorescent tube driving circuit of claim 23, further comprising a frequency adjusting circuit for adjusting an operating frequency of the control circuit to adjust a power outputted by the converting circuit to the load. The fluorescent tube driving circuit of claim 28, wherein the frequency adjusting circuit is coupled to the input voltage such that the operating frequency varies with the input voltage.